Surgery is characterized by a continuous search towards minimal invasiveness.
Since the 1980s open surgery is largely replaced by an endoscopic approach in which long instruments are inserted through trocars in a CO2 extended abdomen.
Laparoscopic surgery, known for its validated benefits of shorter hospitalization, less postoperative pain and earlier recovery, is more demanding for the surgeon.
Precise dissection, suturing and knot tying in minimal access surgery is an advanced skill. Especially when the suture line and the axis of the needle holder are unparallel this skill is difficult to master.
Recent steps in the evolution towards minimal invasiveness are Single Port Surgery (SPS) and Natural Orifice Transluminal Endoscopic Surgery (NOTES). Both approaches result in a scarless healing. In SPS the instruments are inserted through one big trocar through e.g. the umbillicus. NOTES is a surgical technique whereby abdominal operations are performed with an endoscope passed through a natural orifice e.g. mouth through an internal incision in the stomach, bladder or colon. In these procedures surgery is made more challenging by the spatial constraints and the lack of triangulation.
A disadvantage of endoscopic surgery is reduced dexterity for the surgeon. This is mainly because of the fulcrum effect and the absence of wrist like movements at the tip of the instrument. Awareness of this disadvantage increases as more complex endoscopic procedures and single port surgeries (characterized by sword fighting of the instruments) are performed.
The fulcrum effect is explained by the long instruments that pivot at the level of the trocar inserted in the abdomen. A movement of the handle to the left is translated in a movement to the right at the effector (e.g. a pair of scissors). It is surprising to see how fast surgeons adapt to these inversed movements.
The lack of wrist-like movements is more difficult to overcome. A state-of-the-art solution is provided by the Da Vinci robot (Intuitive Surgical). In this master slave system all the movements of the surgeons' hands at the console are transferred to fluent movements at the instruments' tip. This solution is quite expensive, leading to the development of cheaper hand instruments with an omni-directional articulated tip.
Most of the challenge is explained by the reduced dexterity. A conventional rigid laparoscopic instrument offers only 4 degrees of freedom (rotation, up/down angulations, left/right angulations, in/out movements).
To overcome this restriction in movements, various designs for steerable instruments have been developed:
1. In its simplest form an articulated instruments consist of a prebent flexible tube sliding out of a rigid straight tube (uni-directional articulated instruments). This tip can only bend in one direction and cannot withstand an appropriate amount of lateral force. In another solution the instrument tip is operated via gear trains FIG. 9.
2. More advanced alternatives are instruments that allow bending movements of the tip in one plane e.g. left to right and vice versa FIG. 8-10. Because of the nature of the construction, a mostly stable tip is created. These bi-directional instruments need to be navigated to a point of interest by bending into one direction and then by turning the whole instrument around its own axis. This is not intuitive.
3. True wrist movements are only possible with omni-directional systems FIG. 11-17. The omnidirectional articulated instruments consist mainly of a proximal and distal end, a proximal and distal bending part and an intermediate part in between. Movement of the proximal end is transferred to a movement at the distal end.
Examples are described in U.S. Pat. No. 7,410,483 FIG. 11 and U.S. Pat. No. 8,105,350 FIG. 15.
Similar to robotic surgery, omni-directional articulated instruments provide 7 degrees of freedom (axial rotation and deflection of the tip in two planes are added to the 4 DOF of conventional rigid instruments). A combination of up/down and left/right movements at the proximal side allows to reach any point at the distal effector side without the need for a rotation around its own axis.
The increased maneuverability is paid back by a serious decrease in tip stability. To solve this, hybrid solutions such as the Kymerax® system (Terumo) and Jaimy® system (EndoControl) compensate by using strong electrical motors to restore the tip stability. In US Patent Application Pub. No.: US 2011/0004157 an alternative solution to provide an appropriate tip stability is presented. The steering mechanism is based on a tubular structure with longitudinal cuts.
Omni-directional articulated instruments offer, in comparison to robotic systems the advantages of low costs and tactile feedback.
Nevertheless all these omni-directional articulated instruments are prone to crosstalk, a conflict of two different movements FIG. 21.
Bending the proximal zone 202, in order to deflect the distal tip of the instrument 205, will result in an additional unintended swinging of the whole instrument around its fulcrum point at the level of the trocar 221 in the abdomen FIG. 21. The distal tip 205 will move to the opposite direction.
In other words, to adjust the direction of the articulated tip 205, the orientation of the surgeon hand needs to be changed. This is possible by a rotation of the surgeons' hand around the surgeons' wrist FIG. 21. However this also results in a movement of the proximal bendable part 202 around the surgeons' wrist. The latter will result in a movement of the whole instrument around the fulcrum at the level of the trocar 221 in the abdomen.
The surgeons' hand movements are thus involved in the position of the articulated tip as well as in the direction of the whole instrument.
A prior art solution to overcome the problem of crosstalk is disclosed in U.S. Pat. No. 8,105,350 FIG. 15. A “locking” feature 150 to keep the tip of the instrument at a constant angle is used. Once the surgeon has the instrument tip in the desired bent position the angle is locked. Thereafter the instrument is further used as a conventional prebent instrument. This results in a complete loss of intuitive wrist like movements.
A second prior art solution to overcome the problem of crosstalk is the use of thumb-controlled (using a small joystick) instruments FIG. 12 instead of wrist-controlled instruments FIG. 11. This has recently be researched by Linde M. Okken. In Surg Endosc (2012) 26:1977-1985 she advocates that thumb control is more suitable for steerable instruments than wrist control to avoid uncontrolled movements. Mostly an additional “locking” feature is mandatory. The thumb-controlled way of steering an instrument is not intuitive.
The crosstalk is thus the result of a rotation point at the surgeons' wrist 223 laying far proximal from the rotation point at the proximal bending part 222 of the steerable instrument FIG. 20.
The longer the distance between the rotation point at the surgeons' wrist 223 and the rotation point at the proximal bending part 222 of the steerable instrument the more crosstalk.
In standard in-line handles the distance is around 260 mm FIG. 20A, for a standard pistol grip handle 200 mm FIG. 20B.
Accordingly, an object of the present invention is to provide an improved endoscopic surgical instrument in which the distance between the rotation point at the surgeons' wrist 223 and the rotation point at the proximal bending part 222 is reduced in order to reduce crosstalk and thus leading to more intuitive movements and enhanced dexterity.